Touch sensor, display device, and electronic apparatus

ABSTRACT

A touch sensor includes a sensor electrode having an electrostatic capacitance for touch detection, and a touch detection circuit detecting a contact or proximity position of an object on the basis of a detection signal obtained from the sensor electrode by applying a touch sensor drive signal to the sensor electrode. The sensor electrode is split into plural stripe-like electrode patterns. Applying the touch sensor drive signal to part of the electrode patterns forms a drive line at that time. The touch detection circuit performs a detection on the basis of a first detection signal obtained from a first drive line formed in a first period, and a second detection signal obtained from a second drive line formed in a second period.

CROSS REFERENCES TO RELATED APPLICATIONS

The present application is a Continuation of application Ser. No.12/662,976, filed May 13, 2010, which claims priority to Japanese PatentApplication JP 2009-126487 filed in the Japanese Patent Office on May26, 2009. The entire contents of these applications are incorporatedherein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a display device such as a liquidcrystal display device, in particular, a capacitive touch sensor thatallows a user to input information by bringing a finger or the like intocontact with or proximity to the touch sensor, and a display device andan electronic apparatus including such a touch sensor.

2. Description of the Related Art

Recently, attention has been paid to a type of display device which hasa contact detecting device (hereinafter, referred to as touch sensor) ora so-called touch panel directly mounted on a liquid crystal displaydevice, and in which various buttons are displayed on the liquid crystaldisplay device instead of ordinary buttons to allow input ofinformation. Since this technology enables shared placement of thedisplay and buttons amid the growing tendency toward larger screen sizesof mobile apparatus, the technology provides significant advantages suchas space saving and reduced number of parts. However, this technologyhas a problem in that the overall thickness of the liquid crystal moduleincreases due to the mounting of the touch sensor. In particular, inmobile apparatus applications, a protective layer is necessary forprotecting the touch sensor from scratches. Thus, the liquid crystalmodule tends to become increasingly thicker, which goes against thetrend toward reduced thickness.

Accordingly, for example, Japanese Unexamined Patent ApplicationPublication No. 2008-9750 and U.S. Pat. No. 6,057,903 each propose aliquid crystal display element with a touch sensor in which a capacitivetouch sensor is formed, thus achieving reduced thickness. In this liquidcrystal display element with a touch sensor, a conductive film for touchsensor is provided between the observation-side substrate of the liquidcrystal display element, and a polarizing plate for observation arrangedon the outer surface thereof, and a capacitive touch sensor is formedbetween the conductive film for touch sensor, and the outer surface ofthe polarizing plate, with the outer surface of the polarizing plateserving as a touch surface. In addition, for example, JapaneseUnexamined Patent Application Publication (Translation of PCTApplication) No. 56-500230 proposes a structure in which a touch sensoris built in a display device.

SUMMARY OF THE INVENTION

However, in the liquid crystal display element with a touch sensordisclosed in each of Japanese Unexamined Patent Application PublicationNo. 2008-9750 and U.S. Pat. No. 6,057,903, in principle, it is necessarythat the conductive film for touch sensor be set at the same potentialas that of the user, and thus it is necessary that the user be properlygrounded. Therefore, aside from stationary television receivers whichdraw power from a socket, realistically, it is difficult to use such aliquid crystal device display element for mobile apparatus applications.In addition, according to the technique mentioned above, since it isnecessary that the conductive film for touch sensor be located veryclose to the user's finger, there are limits to the location where theconductive film can be disposed, such that it is not possible to disposethe conductive film in a deeper portion of the liquid crystal displayelement, for example. That is, the degree of freedom of design is small.Further, the configuration according to the above-mentioned techniquemakes it necessary to provide circuit portions such as a touch sensordrive portion and a coordinate detecting portion separately from adisplay drive circuit portion for the liquid crystal display element,making it difficult to achieve circuit integration for the apparatus asa whole.

Accordingly, a conceivable solution would be to provide, in addition toa common electrode originally provided for applying a display drivevoltage, a touch detection electrode that forms an electrostaticcapacitance between the common electrode and the touch detectionelectrode (a display device including a capacitive touch sensor of anovel structure). That is, since this electrostatic capacitance changesdepending on the presence/absence of contact or proximity of an object,if a display drive voltage applied to the common electrode by a displaycontrol circuit is also used (doubled) as a touch sensor drive signal, adetection signal responsive to a change in electrostatic capacitance isobtained from the touch detection electrode. Then, if this detectionsignal is inputted to a predetermined touch detection circuit, it ispossible to detect the presence/absence of contact or proximity of anobject. In addition, according to this technique, it is possible toobtain a display device with a touch sensor which can be even adaptedfor mobile apparatus applications in which the electric potential on theuser side is often inconstant. Further, there are also advantages inthat it is possible to obtain a display device with a touch sensorhaving a high degree of design freedom in accordance with the type ofdisplay function layer, and integration of circuits for display andcircuits for sensor on a single circuit board is also facilitated,allowing for easy circuit integration.

The problem with capacitive touch sensors, including those according toJapanese Unexamined Patent Application Publication No. 2008-9750, U.S.Pat. No. 6,057,903, and Japanese Unexamined Patent ApplicationPublication (Translation of PCT Application) No. 56-500230 mentionedabove, and the above-mentioned novel structure, is that when writing apixel signal (image signal) to the display element at each pixel, noise(internal noise) resulting from the writing operation is added to thedetection signal.

Accordingly, to prevent erroneous operation (erroneous detection) due tonoise resulting from the image signal writing operation, according toU.S. Pat. No. 6,057,903 and Japanese Unexamined Patent ApplicationPublication (Translation of PCT Application) No. 56-500230 mentionedabove, a transparent conductive layer (shield layer) is provided betweenthe touch sensor and the display element. Then, by fixing thisconductive layer to a constant potential, it is possible to shieldagainst the above-mentioned noise from the display element.

However, this technique has a problem in that since a large capacitanceis formed between the detection signal wire and the shield layer, thedetection signal obtained from the detection signal wire issignificantly attenuated, or the capacitance on the drive wire becomesso large that power consumption significantly increases. In addition, asin Japanese Unexamined Patent Application Publication (Translation ofPCT Application) No. 56-500230 mentioned above, in the case where adetection signal for touch sensor is generated by using a part of thedisplay drive circuit, when a shield layer is arranged between thedisplay element and the detection electrode, the detection signal isalso shielded out, making it difficult to perform a detection.

Further, as described above, the display device including a capacitivetouch sensor according to the above-mentioned novel structure detects aposition by using a write waveform in the display panel. For thisreason, from the viewpoint of aperture ratio and manufacturing process,it is considered difficult to remove noise resulting from an imagesignal writing operation by providing a shield layer within theeffective display area.

As described above, in the case of capacitive touch sensors, it isdifficult to improve the accuracy of object detection by removing noise(internal noise) resulting from an image signal writing operationwithout using a shield layer, for example.

It is desirable to provide a capacitive touch sensor that makes itpossible to improve the accuracy of object detection, and a displaydevice and an electronic apparatus including such a touch sensor.

A touch sensor according to one embodiment includes a sensor electrodehaving an electrostatic capacitance for touch detection, and a touchdetection circuit detecting a contact or proximity position of an objecton the basis of a detection signal obtained from the sensor electrode byapplying a touch sensor drive signal to the sensor electrode. The sensorelectrode is split into plural stripe-like electrode patterns. Applyingthe touch sensor drive signal to part of the electrode patterns forms adrive line at that time. The touch detection circuit performs adetection on the basis of a first detection signal obtained from a firstdrive line formed in a first period, and a second detection signalobtained from a second drive line formed in a second period.

A touch sensor according to another embodiment includes a touch driveelectrode, a touch detection electrode provided in opposition to or sideby side with the touch drive electrode and forming an electrostaticcapacitance between the touch detection electrode and the touch driveelectrode, and a touch detection circuit that performs a detection of acontact or proximity position of an object, on the basis of a detectionsignal obtained from the touch detection electrode by applying a touchsensor drive signal to the touch drive electrode. The touch driveelectrode is split into a plurality of electrode patterns in a stripeshape, and application of the touch sensor drive signal to part of theplurality of electrode patterns causes a drive line to be formed at thattime. The touch detection circuit performs the detection on the basis ofa first detection signal obtained from a first drive line formed in afirst period, and a second detection signal obtained from a second driveline formed in a second period different from the first period andhaving a smaller line width than the first drive line.

A display device according to an embodiment of the present inventionincludes a plurality of display pixel electrodes, a common electrodeprovided in opposition to the display pixel electrodes, a displayfunction layer having an image display function, a display controlcircuit that controls image display on the basis of an image signal soas to apply a display drive voltage between the display pixel electrodesand the common electrode to cause the display function layer to exertthe image display function, on the basis of an image signal, a touchdetection electrode provided in opposition to or side by side with thecommon electrode and forming an electrostatic capacitance between thetouch detection electrode and the common electrode, and a touchdetection circuit that performs a detection of a contact or proximityposition of an object, on the basis of a detection signal obtained fromthe touch detection electrode, by using the display drive voltageapplied to the common electrode by the display control circuit as atouch sensor drive signal. The common electrode is split into aplurality of electrode patterns in a stripe shape, and application ofthe touch sensor drive signal to part of the plurality of electrodepatterns causes a drive line to be formed at that time. The touchdetection circuit performs the detection on the basis of a firstdetection signal obtained from a first drive line formed in a firstperiod, and a second detection signal obtained from a second drive lineformed in a second period different from the first period and having asmaller line width than the first drive line.

An electronic apparatus according to an embodiment of the presentinvention includes the above-mentioned display device according to anembodiment of the present invention.

In the touch sensor, the display device, and the electronic apparatusaccording to an embodiment of the present invention, an electroniccapacitance is formed between the common electrode or the touch driveelectrode originally provided for applying the display drive voltage,and the touch detection electrode. This electrostatic capacitancechanges depending on the presence/absence of contact or proximity of anobject. Therefore, by using the touch sensor drive signal applied to thecommon electrode or the touch drive electrode, a detection signalresponsive to a change in electrostatic capacitance is obtained from thetouch detection electrode. Then, by inputting this detection signal tothe touch detection circuit, the contact or proximity position of anobject (the presence/absence of contact or proximity of an object) isdetected. At this time, the touch detection circuit performs a detectionon the basis of the first detection signal obtained from the first drivesignal formed in the first period, and the second detection signalobtained from the second drive line formed in the second perioddifferent from the first period. Since the line width of the seconddrive line is smaller than the line width of the first drive line, byusing the first detection signal and the second detection signalobtained from the respective lines (for example, by taking thedifference between the two detection signals), a detection can beperformed while reducing the influence of noise (internal noise)contained in the detection signal due to an image signal writingoperation at the time of image display control.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A and 1B are diagrams for explaining the operation principle of adisplay device with a touch sensor according to an embodiment of thepresent invention, showing a state when a finger is not in contact;

FIGS. 2A and 2B are diagrams for explaining the operation principle of adisplay device with a touch sensor according to an embodiment of thepresent invention, showing a state when a finger is in contact;

FIGS. 3A and 3B are diagrams for explaining the operation principle of adisplay device with a touch sensor according to an embodiment of thepresent invention, showing an example of the waveforms of a drive signaland detection signal of a touch sensor;

FIG. 4 is a cross-sectional view showing the schematic cross-sectionalstructure of a display device with a touch sensor according to a firstembodiment of the present invention;

FIG. 5 is a perspective view showing an example of the configuration ofthe main portion (a common electrode and a sensor detection electrode)of the display device shown in FIG. 4;

FIG. 6 is a block diagram showing an example of the pixel structure anddetailed driver configuration in the display device shown in FIG. 4;

FIG. 7 is a block diagram showing another example of the pixel structureand detailed driver configuration in the display device shown in FIG. 4;

FIG. 8 is a circuit diagram showing an example of the configuration of adetection circuit and the like in the display device shown in FIG. 4;

FIGS. 9A to 9C are schematic diagrams showing an example of linesequential operation drive of a common electrode;

FIGS. 10A to 10F are timing waveform diagrams for explaining noise(internal noise) resulting from a display writing operation at the timeof a detection in a display device;

FIGS. 11A and 11B are timing diagrams for explaining an example of aninternal noise removal method according to the first embodiment;

FIGS. 12A and 12B are timing waveform diagrams showing an example of thewaveforms of a detection signal and noise signal at the time of theinternal noise removal shown in FIGS. 11A and 11B;

FIGS. 13A and 13B are timing waveform diagrams showing an example of thewaveform of a noise signal at the time of the internal noise removalshown in FIGS. 11A and 11B;

FIGS. 14A to 14C are timing waveform diagrams showing an example of thewaveforms at the time of writing white and at the time of writing blackin case in which the internal noise removal method shown in FIGS. 11Aand 11B is applied;

FIGS. 15A and 15B are timing diagrams for explaining an internal noiseremoval method according to a modification of the first embodiment;

FIG. 16 is a cross-sectional view showing the schematic cross-sectionalstructure of a display device with a touch sensor according to a secondembodiment of the present invention;

FIGS. 17A and 17B are respectively a cross-sectional view and a planview showing the detailed configuration of a part of a pixel substratein the display device shown in FIG. 16;

FIGS. 18A and 18B are exploded perspective views of the main portion ofthe display device shown in FIG. 16;

FIGS. 19A and 19B are cross-sectional views for explaining the operationof the display device shown in FIG. 16;

FIG. 20 is a cross-sectional view showing the schematic cross-sectionalstructure of a display device with a touch sensor according to amodification of the second embodiment;

FIG. 21 is a cross-sectional view showing the schematic cross-sectionalstructure of a display device with a touch sensor according to anothermodification of the second embodiment;

FIG. 22 is a perspective view showing the outward appearance ofApplication 1 of the display device according to each of the aboveembodiments and the like;

FIGS. 23A and 23B are a perspective view as seen from the front side anda perspective view as seen from the back side, respectively, ofApplication 2;

FIG. 24 is a perspective view showing the outward appearance ofApplication 3;

FIG. 25 is a perspective view showing the outward appearance ofApplication 4;

FIGS. 26A to 26G are a front view of Application 5 when open, a sideview thereof, a front view when closed, a left side view, a right sideview, a top view, and a bottom view, respectively;

FIGS. 27A and 27B are timing diagrams for explaining an internal noiseremoval method according to a modification of an embodiment of thepresent invention;

FIG. 28 is a cross-sectional view showing the main-portion configurationof a touch sensor according to another modification of an embodiment ofthe present invention; and

FIG. 29 is a schematic diagram showing an example of drive lines in thetouch sensor shown in FIG. 28.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinbelow, embodiments of the present invention will be described indetail with reference to the drawings. It should be noted that thedescription will be given in the following order of topics.

Basic Principle of Touch Detection System

1. First Embodiment (an example of internal noise removal method usingtwo drive lines of different widths)

2. Second Embodiment (an example using a liquid crystal element of atransverse electric field mode as a display element)

3. Applications (applications of a display device with a touch sensor toan electronic apparatus)

4. Other Modifications

<Basic Principle of Touch Detection System>

First, referring to FIGS. 1A to 3B, a description will be given of thebasic principle of a touch detection system in a display device with atouch sensor according to an embodiment of the present invention. Thistouch detection system is to be implemented as a capacitive touchsensor. For example, as shown in FIG. 1A, a capacitor is formed by usinga pair of electrodes (a drive electrode E1 and a detection electrode E2)opposed to each other with a dielectric D therebetween. This structureis represented as an equivalent circuit shown in FIG. 1B. A capacitor C1is formed by the drive electrode E1, the detection electrode E2, and thedielectric D. One end of the capacitor C1 is connected to an AC signalsource (drive signal source) S, and the other end P is grounded via aresistor R, and connected to a voltage detector (detection circuit) DET.When an AC rectangular wave Sg (FIG. 3B) of a predetermined frequency(for example, about several kHz to ten and several kHz) is applied fromthe AC signal source S to the drive electrode E1 (one end of thecapacitor C1), an output waveform (detection signal Vdet) as shown inFIG. 3A appears in the detection electrode E2 (the other end P of thecapacitor C1). It should be noted that this AC rectangular wave Sgcorresponds to a common drive signal Vcom described later.

In a state when the finger is not in contact (or proximity), as shown inFIG. 1B, a current I0 varying with the capacitance value of thecapacitor C1 flows as the capacitor C1 is charged and discharged. Thepotential waveform at the other end P of the capacitor C1 at this timebecomes as indicated by the waveform V0 in FIG. 3A, for example, whichis detected by the voltage detector DET.

On the other hand, in a state when the finger is in contact (orproximity), as shown in FIGS. 2A and 2B, a capacitor C2 formed by thefinger is added in series to the capacitor C1. In this state, currentsI1, I2 flow as the capacitors C1, C2 are charged and discharged,respectively. The potential waveform at the other end P of the capacitorC1 at this time becomes as indicated by the waveform V1 in FIG. 3A, forexample, which is detected by the voltage detector DET. At this time,the potential at the point P is a partial potential determined by thevalues of the currents I1, I2 flowing in the capacitors C1, C2. Thus,the waveform V1 becomes smaller in value than the waveform V0 in thenon-contact state. As will be described later, the voltage detector DETcompares the detected voltage with a predetermined threshold voltageVth, and judges the current state to be a non-contact state if thedetector voltage is equal to or greater than this threshold voltage. Onthe other hand, the voltage detector DET judges the current state to bea contact state if the detector voltage is less than the thresholdvoltage. In this way, touch detection becomes possible.

1. First Embodiment Example of Configuration of Display Device 1

FIG. 4 shows the cross-sectional structure of the main portion of adisplay device 1 with a touch sensor according to a first embodiment ofthe present invention. In the display device 1, a capacitive touchsensor is formed by using a liquid crystal display element as a displayelement, and sharing the use of part (common electrode 43 describedlater) of electrodes originally provided to this liquid crystal displayelement and a display drive signal (common drive signal Vcom describedlater).

As shown in FIG. 4, the display device 1 includes a pixel substrate 2, acounter substrate 4 opposed to the pixel substrate 2, and a liquidcrystal layer 6 inserted between the pixel substrate 2 and the countersubstrate 4.

The pixel substrate 2 has a TFT substrate 21 as a circuit board, and aplurality of pixel electrodes 22 disposed in matrix on the TFT substrate21. In addition to display drivers and TFTs (thin film transistors) (notshown) for driving the individual pixel electrodes 22, wires such assource wires (source wires 25 described later) for supplying imagesignals to the individual pixel electrodes, and gate wires (gate wires26 described later) for driving individual TFTs are formed on the TFTsubstrate 21. A detection circuit (FIG. 8) that performs a touchdetection described later may be also formed on the TFT substrate 21.

The counter substrate 4 includes a glass substrate 41, a color filter 42formed on one surface of the glass substrate 41, and a common electrode43 formed on the color filter 42. The color filter 42 is formed byperiodically arranging color filter layers of three colors, for example,red (R), green (G), and blue (B). A set of the three colors of R, G, andB is associated with each of display pixels (pixel electrodes 22). Thecommon electrode 43 also doubles as a sensor drive electrodeconstituting a part of the touch sensor for performing a touchdetection, and corresponds to the drive electrode E1 shown in FIG. 1A.

The common electrode 43 is coupled to the TFT substrate 21 by a contactconductive column 7. A common drive signal Vcom having an AC rectangularwaveform is applied from the TFT substrate 21 to the common electrode 43via the contact conductive column 7. While this common drive signal Vcomdefines the display voltage of each pixel together with a pixel voltageapplied to each of the pixel electrodes 22, the common drive signal Vcomalso doubles as a drive signal for the touch sensor, and corresponds tothe AC rectangular wave Sg supplied from the drive signal source S shownin FIGS. 1A and 1B. That is, the common drive signal Vcom is inverted inpolarity at every predetermined cycle.

A sensor detection electrode (touch detection electrode) 44 is formed onthe other surface of the glass substrate 41. Further, a polarizing plate45 is disposed on the sensor detection electrode 44. The sensordetection electrode 44 constitutes a part of the touch sensor, andcorresponds to the detection electrode E2 shown in FIG. 1A.

The liquid crystal layer 6 modulates light passing through the liquidcrystal layer 6 in accordance with the state of the electric field. Forexample, a liquid crystal of various modes such as TN (Twisted Nematic),VA (Vertical Alignment), and ECB (Electrically Controlled Birefringence)is used for the liquid crystal layer 6.

An alignment film is disposed between the liquid crystal layer 6 and thedrive substrate 2, and between the liquid crystal layer 6 and thecounter substrate 4, and an incidence-side polarizing plate is arrangedon the lower surface side of the pixel substrate 2. However,illustration of these components is omitted here.

(Exampled of Detailed Configuration of Common Electrode 43 and SensorDetection Electrode 44)

FIG. 5 illustrates an example of the configuration of the commonelectrode 43 and the sensor detection electrode 44 in the countersubstrate 4 in perspective view. In this example, the common electrode43 is split into a plurality of stripe-like electrode patterns (here,for example, n(n: an integer not smaller than 2) common electrodes 431to 43 n) extending in the horizontal direction of the drawing. Thecommon drive signal Vcom is sequentially supplied by a common electrodedriver 43D to each electrode pattern, thereby performing a linesequential scanning drive in a time division manner as will be describedlater. On the other hand, the sensor detection electrode 44 includes aplurality of stripe-like electrode patterns extending in a directionorthogonal to the direction in which the electrode patterns of thecommon electrode 43 extend. A detection signal Vdet is outputted fromeach of the electrode patterns of the sensor detection electrode 44, andinputted to the detection circuit 8 shown in FIGS. 6 to 8 and the like.

(Example of Pixel Structure and Configuration of Drivers)

FIGS. 6 and 7 each show an example of pixel structure and configurationof various drivers in the display device 1. In the display device 1, aplurality of pixels (display pixels 20) each having a TFT element Tr anda liquid crystal element LC are arranged in matrix inside an effectivedisplay area 100.

In the example shown in FIG. 6, the gate wires 26 connected to a gatedriver 26D, the signal wires (source wires) 25 connected to a sourcedriver (not shown), and the common electrodes 431 to 43 n connected tothe common electrode driver 43D are connected to the display pixels 20.As described above, the common electrode driver 43 sequentially suppliesthe common drive signal Vcom(Vcom(1) to Vcom(n)) to the commonelectrodes 431 to 43 n. The common electrode driver 43D has, forexample, a shift register 43D1, a COM selector section 43D2, a levelshifter 43D3, and a COM buffer 43D4.

The shift register 43D1 is a logic circuit for sequentially transferringan input pulse. Specifically, clock transfer is started by inputting atransfer trigger pulse (start pulse) to the shift register 43D1. In thecase when the start pulse is inputted a plurality of times within asingle frame period, transfer can be repeated every time such an inputis made. It should be noted that the shift register 43D1 may beconfigured as independent transfer logic circuits for individuallycontrolling the plurality of common electrodes 431 to 43 n. It should benoted, however, that since the control circuit scale increases in thatcase, as shown in FIG. 7 described later, it is preferable that thetransfer logic circuit be shared by the gate driver and the commonelectrode driver, and it is further preferable that the transfer logiccircuit be unitary irrespective of the number of the common electrodes43.

The COM selector section 43D2 is a logic circuit that performs a controlof whether or not to output the common drive signal Vcom to each of thedisplay pixels 20 within the effective display area 100. That is, theCOM selector section 43D2 controls the output of the common drive signalVcom in accordance with the position or the like within the effectivedisplay area 100. Further, although will be described later in detail,by making the control pulse inputted to the COM selector section 43D2variable, it is possible, for example, to arbitrarily move the outputposition of the common drive signal Vcom on a per horizontal line basis,or to move the output position after a plurality of horizontal periods.

The level shifter 43D3 is a circuit for shifting a control signalsupplied from the COM selector section 43D2 to a potential levelsufficient for controlling the common drive signal Vcom.

The COM buffer 43D4 is a final output logic circuit for sequentiallysupplying the common drive signal Vcom(Vcom(1) to Vcom(n)), and includesan output buffer circuit, a switching circuit, and the like.

On the other hand, in the example shown in FIG. 7, the gate wires 26 andthe common electrodes 431 to 43 n connected to a gate/common electrodedriver 40D, and the signal wires (source wires) 25 connected to a sourcedriver (not shown) are connected to the display pixels 20. Thegate/common electrode driver 40D supplies a gate drive signal to each ofthe display pixels 20 via the gate wires 26, and sequentially suppliesthe common drive signal Vcom (Vcom(1) to Vcom(n)) to each of the commonelectrodes 431 to 43 n. The gate/common electrode driver 40D has, forexample, a shift register 40D1, an enable control section 40D2, agate/COM selector section 40D3, a level shifter 40D4, and a gate/COMbuffer 40D5.

The shift register 40D1 has the same function as the shift register 43D1described above except that the shift register 40D1 is shared by thegate driver and the common electrode driver.

The enable control section 40D2 generates a pulse for controlling thegate wires 26 by taking in an enable pulse by using a clock pulsetransferred from the shift register 40D1.

The gate/COM selector section 40D3 is a logic circuit that performs acontrol of whether or not to output the common drive signal Vcom and agate signal VG to each of the display pixels 20 within the effectivedisplay area 100. That is, the gate/COM selector section 40D3 controlsthe respective outputs of the common drive signal Vcom and gate signalVG in accordance with the position or the like within the effectivedisplay area 100.

The level shifter 40D4 is a circuit for shifting a control signalsupplied from the gate/COM selector section 40D3 to a potential levelsufficient for controlling the gate signal VG and the common drivesignal Vcom.

The gate/COM buffer 40D5 is a final output logic circuit forsequentially supplying the common drive signal Vcom(Vcom(1) to Vcom(n))and the gate signal VG(VG(1) to VG(n)), and includes an output buffercircuit, a switching circuit, and the like.

In the example shown in FIG. 7, a T/G-DC/DC converter 20D is providedwithin the display device 1 in addition to these components. TheT/G-DC/DC converter 20D serves as a TG (timing generator) and a DC/DCconverter.

(Example of Circuit Configuration of Drive Signal Source S and DetectionCircuit 8)

FIG. 8 shows an example of the circuit configuration of the drive signalsource S shown in FIG. 1B and the detection circuit 8 that performs atouch detection, together with a timing control section 9 serving as atiming generator. In this drawing, capacitors C11 to C1 n correspond to(electrostatic) capacitors formed between the individual commonelectrodes 431 to 43 n and the sensor detection electrode 44 shown inFIG. 5.

One drive signal source S is provided for each of the capacitors C11 toC1 n. The drive signal source S has a SW control section 11, twoswitching elements 12, 15, two inverter (NOT) circuits 131, 132, and anoperational amplifier 14. The SW control section 11 controls the ON/OFFstate of the switching element 12, thereby controlling the connectionstate between a power supply+V and the inverter circuits 131, 132. Theinput terminal of the inverter circuit 131 is connected to one end(terminal on the side opposite to the power supply+V) of the switchingelement 12 and the output terminal of the inverter circuit 132. Theoutput terminal of the inverter circuit 131 is connected to the inputterminal of the inverter circuit 132 and the input terminal of theoperational amplifier 14. Thus, the inverter circuits 131, 132 eachfunction as an oscillating circuit for outputting a predetermined pulsesignal. The operational amplifier 14 is connected to the two powersupplies +V, −V. The ON/OFF state of the switching element 15 iscontrolled in accordance with a timing control signal CTL1 supplied fromthe timing control section 9. Specifically, one end side (the commonelectrodes 431 to 43 n side) of the capacitors C11 to C1 n is connectedto the outer terminal side (the supply source side of the common voltagesignal Vcom) of the operational amplifier 14 or the ground. Thus, thecommon drive signal Vcom is supplied from each of the drive signalsources S to each of the capacitors C11 to C1 n.

The detection circuit 8 (voltage detector DET) has an amplifying section81, an A/D (analog/digital) conversion section 83, a signal processingsection 84, a frame memory 86, a coordinate extracting section 85, andthe resistor R described above. It should be noted that the inputterminal Tin of the detection circuit 8 is connected commonly to theother end side (the sensor detection electrode 44 side) of thecapacitors C11 to C1 n.

The amplifying section 81 is a section that amplifies the detectionsignal Vdet inputted from the input terminal Tin, and has an operationalamplifier 811 for signal amplification, two resistors 812R, 813R, andtwo capacitors 812C, 813C. The positive input end (+) of the operationalamplifier 811 is connected to the input terminal Tin, and the output endis connected to the input end of the A/D conversion section 83 describedlater. One ends of the resistor 812R and the capacitor 812C are bothconnected to the output end of the operational amplifier 811, and theother ends of the resistor 812R and the capacitor 812C are bothconnected to the negative input end (−) of the operational amplifier811. In addition, one end of the resistor 813R is connected to the otherends of the resistor 812R and the capacitor 812C, and the other end ofthe resistor 813R is connected to the ground via the capacitor 813C.Thus, the resistor 812R and the capacitor 812C function as a low-passfilter (LPF) that cuts high frequencies and passes low frequencies, andthe resistor 813R and the capacitor 813C function as a high-pass filter(HPF) that passes high frequencies.

The resistor R is arranged between a node P on the positive input end(+) side of the operational amplifier 811, and the ground. The resistorR is provided to maintain a stable state by avoiding floating of thesensor detection electrode 44. This not only prevents fluctuations inthe signal value of the detector signal Vdet in the detection circuit 8,but also provides an advantage of releasing static electricity to theground via the resistor R.

The A/D conversion section 83 converts the analog detection signal Vdetamplified by the amplifying section 81 into a digital detection signal,and includes a comparator (not shown). This comparator compares thepotentials of an inputted detection signal and the predeterminedthreshold voltage Vth (see FIGS. 3A and 3B). It should be noted that thesampling timing at the time of A/D conversion in the A/D conversionsection 83 is controlled by a timing control signal CTL2 supplied fromthe timing control section 9.

The signal processing section 84 applies predetermined signal processing(for example, signal processing such as digital noise removal, orconversion of frequency information into positional information) to adigital detection signal outputted from the A/D conversion section 83.Although described later in detail, the signal processing section 84 isalso configured to perform predetermined arithmetic processing forremoving (suppressing) the influence of noise (internal noise) resultingfrom an image signal writing operation, together with the frame memory86.

The coordinate extracting section 85 obtains a detection result (whetheror not a touch has been made, and the position coordinates of the touchlocation if a touch has been made) on the basis of a detection signal (adetection signal that has undergone the internal noise removal mentionedabove) outputted from the signal processing section 84, and outputs thedetection result from the output terminal Tout.

It should be noted that the above-mentioned detection circuit 8 may beformed in a peripheral region (non-display region or rim region) on thecounter substrate 4, or may be formed in a peripheral region on thepixel substrate 2. However, forming the detection circuit 8 on the pixelsubstrate 2 is more preferable from the viewpoint of achievingsimplification by circuit integration, because it is possible to achieveintegration with various circuit elements and the like for displaycontrol originally formed on the pixel substrate 2. In this case, eachelectrode pattern of the sensor detection electrode 44 and the detectioncircuit 8 on the pixel substrate 2 may be connected to each other by acontact conductive column (not shown) similar to the contact conductivecolumn 7, and the detection signal Vdet may be transmitted from thesensor detection electrode 44 to the detection circuit 8.

[Operation/Effect of Display Device 1]

Next, the operation and effect of the display device 1 according to thisembodiment will be described.

(Basic Operation)

In the display device 1, a display driver (such as the common electrodedriver 43D) on the pixel substrate 2 supplies the common drive signalVcom in a line sequential manner to each of the electrode patterns(common electrodes 431 to 43 n) of the common electrode 43. This displaydriver also supplies pixel signals (image signals) to the pixelelectrodes 22 via the source wires 25, and in synchronization with this,controls the switching of the TFTs (TFT elements Tr) of the pixelelectrodes via the gate wires 26 in a line sequential manner. Thus, anelectric field in the vertical direction (direction perpendicular to thesubstrate) determined by the common drive signal Vcom and each imagesignal is applied to the liquid crystal layer 6 for each display pixel20, thereby modulating the liquid crystal state. In this way, display bythe so-called inversion drive is performed.

On the other hand, on the side of the counter substrate 4, the capacitorC1 (capacitors C11 to C1 n) is formed at each of the intersectionsbetween the individual electrode patterns of the common electrode 43 andthe individual electrode patterns of the sensor detection electrode 44.At this time, the following occurs when, as indicated by the arrow(scanning direction) in FIG. 5, for example, the common drive signalVcom is sequentially applied in a time division manner to each of theelectrode patterns of the common electrode 43. That is, charging anddischarging are performed with respect to each of a row of capacitorsC11 to C1 n formed at the intersections between the electrode pattern ofthe common electrode 43 to which the common drive signal Vcom has beenapplied, and the individual electrode patterns of the sensor detectionelectrode 44. As a result, the detection signal Vdet of a magnitudevarying with the capacitance value of the capacitor C1 is outputted fromeach of the electrode patterns of the sensor detection electrode 44. Ina state when a user's finger is not in touch with the surface of thecounter substrate 4, the magnitude of this detection signal Vdet issubstantially constant. In accordance with the scanning of the commondrive signal Vcom, the row of the capacitors C1 to be charged anddischarged moves in a line sequential manner.

It should be noted that when performing such line sequential driving ofthe electrode patterns of the common electrode 43, for example, as shownin FIGS. 9A to 9C, it is preferable to perform a line sequential drivein batches made up of part of the electrode patterns of the commonelectrode 43. Specifically, drive lines L including this part ofelectrode patterns are made up of a position detection drive line L1including a plurality of lines of electrode patterns, and a displaydrive line L2 including a small number of lines (one line in thisexample) of electrode patterns. This makes it possible to suppress imagequality degradation due to the occurrence of streaks, speckles, or thelike corresponding to the shape of the electrode patterns of the commonelectrode 43.

At this time, when a user's finger touches any one of locations on thesurface of the counter substrate 4, the capacitor C2 due to the fingeris added to the capacitor C1 originally formed at the touch location. Asa result, the detection signal Vdet at the time when the touch locationis scanned (that is, when the common drive signal Vcom is applied to anelectrode pattern corresponding to the touch location among theelectrode patterns of the common electrode 43) becomes smaller in valuethan at other locations. The detection circuit 8 (FIG. 8) compares thisdetection signal Vdet with the threshold voltage Vth, and determines thelocation concerned to be a touch location if the detection signal Vdetis less than the threshold voltage Vth. This touch location can becalculated from the application timing of the common drive signal Vcom,and the detection timing of the detection signal Vdet less than thethreshold voltage Vth.

In this way, in the display device 1 with a touch sensor according tothis embodiment, the common electrode 43 originally provided to theliquid crystal display element doubles as one of a pair of touch sensorelectrodes including a drive electrode and a detection electrode. Inaddition, the common drive signal Vcom as a display drive signal is alsoused as a touch sensor drive signal. Thus, in a capacitive touch sensor,it is necessary to additionally provide only the sensor detectionelectrode 44, and it is unnecessary to prepare a touch sensor drivesignal. Therefore, the configuration is simple.

In the case of the display device with a touch sensor according to therelated art (Japanese Unexamined Patent Application Publication No.2008-9750), the magnitude of a current flowing in the sensor isaccurately measured, and the touch position is determined by analogcomputation on the basis of the measured value. In contrast, in thedisplay device 1 according to this embodiment, it suffices to digitallydetect the presence/absence of a relative change in current (potentialchange) based on the presence/absence of a touch, thereby making itpossible to enhance the detection accuracy by a simple detection circuitconfiguration. In addition, an electrostatic capacitance is formedbetween the common electrode 43 that is originally provided forapplication of the common drive signal Vcom, and the sensor detectionelectrode 44 that is additionally provided, and touch detection isperformed by exploiting the fact that this capacitance changes due tothe contact of a user's finger. Thus, the display device can be alsoadapted for mobile apparatus applications in which the potential on theuser side is often inconstant.

Further, since the sensor detection electrode 44 is split into aplurality of electrode patterns, and the electrode patterns areindividually driven in a time division manner, detection of a touchposition also becomes possible.

(Operation of Characteristic Portion: Detection Using Noise RemovalProcess)

Next, referring to FIGS. 10A to 14C, a detailed description will begiven of a detection using a noise removal process as one ofcharacteristic portions of an embodiment of the present invention.

First, in the case when, as shown in FIG. 10A, the common drive signalVcom undergoes inversion of polarity in synchronism with the drive cycle(1H period) at the time of image display control shown in FIGS. 10B,10C, the detection waveform of the detection signal Vdet becomes asshown in FIGS. 10D to 10F, for example. That is, inversion of polarityis performed in synchronism with this inversion of polarity, and thesignal gradually attenuates after the inversion of polarity due to theleak current flowing in the resistor R described above.

At this time, at the time of pixel signal (image signal) writing such aswhen writing white and when writing black shown in FIGS. 10B, 10C, forexample, noise caused by this writing is contained in the detectionwaveform of the detection signal Vdet as shown in FIGS. 10E, 10F, forexample. Specifically, a 1H period includes a non-writing period ΔtA inwhich no image signal is applied, and a writing period ΔtB in which animage signal is applied. In the writing period ΔtB of these periods,fluctuations occur in the detection waveform in accordance with the graylevel of an image signal. That is, in accordance with the gray level ofthe (polarity-inverted) image signal at that time, noise (internalnoise) caused by the polarity-inverted image signal as indicated by thearrows in FIGS. 10E, 10F is contained in the detection waveform of thedetection signal Vdet. Specifically, noise after inversion is containedin the same phase as the common drive signal Vcom when writing black,and is contained in a phase opposite to the common drive signal Vcomwhen writing white. In this way, in the writing period ΔtB, thedetection waveform of the detection signal Vdet fluctuates due tointernal noise in accordance with the gray level of an image signal,making it difficult to isolate this from the change in detectionwaveform due to the presence/absence of contact of an object (FIG. 3).

Accordingly, in this embodiment, the signal processing section 84, theframe memory 86 and the coordinate extracting section 85 within thedetection circuit 8 performs object detection while removing theabove-mentioned internal noise in the manner as shown in, for example,FIGS. 11A and 11B. Specifically, the signal processing section 84 andthe frame memory 86 perform a process of removing (reducing) noise(internal noise) caused by the image signal mentioned above, on thebasis of two detection signals Vdet respectively obtained from the drivelines L of different line widths in different periods. Then, thecoordinate extracting section 85 performs a detection by using thedetection signal obtained after such noise removal (reduction).

More specifically, in the example shown in FIGS. 11A and 11B, thefollowing control is carried out when line-sequentially driving theposition detection drive line L1 (m(m: an integer not smaller than 2)lines), and the display drive line L2 with a smaller line width (oneline in this example) in the manner as indicated by the arrows in thedrawings. That is, first, in a horizontal period such as T=N, N+2 (N: aninteger) (first period), the timing control section 9 performs a controlsuch that both the position detection drive line L1 with a large linewidth and the display drive line L2 with a small line width exist. Inaddition, in a horizontal period such as T=N+1, N+3 (second period), thetiming control section 9 performs a control such that only the displaydrive line L2 with a small line width exists. In this example shown inFIGS. 11A and 11B, the first period and the second period mentionedabove are set alternately at a time ratio of 1 to 1.

At this time, the waveform of a detection signal Vdet_a (first detectionsignal) obtained from both the position detection drive line L1 and thedisplay drive line L2 becomes as shown in FIG. 12B, for example. Now,let Cp denote the capacitance value of each of the capacitors C11 to C1n, Cc denote the capacitance value of a capacitance component (parasiticcapacitance) other than these capacitors C11 to C1 n, V1 denote theeffective value of an AC voltage due to the AC signal source S, and Vndenote the effective value of a signal inside noise caused by an imagesignal. Then, assuming that Cp equals Cc for the sake of simplicity, thedetection signal Vdet_a obtained in the first period is represented byEquation (1) below. That is, this detection signal Vdet_a includes apotential fluctuation component Va(=(mxV1)/(n+1)) due to the AC signalsource S, and a potential fluctuation component Vb(=Vn) due to noise.

$\begin{matrix}\begin{matrix}{{Vdet\_ a} = {{V\; 1 \times \frac{m \times {Cp}}{{n \times {Cp}} + {Cc}}} + {Vn}}} \\{= {{V\; 1 \times \frac{mCp}{( {n + 1} ){Cp}}} + {Vn}}} \\{= {\frac{m\; V\; 1}{n + 1} + {Vn}}}\end{matrix} & (1)\end{matrix}$

On the other hand, the waveform of a detection signal Vdet_b (seconddetection signal) obtained from only the display drive line L2 in thesecond period becomes as shown in FIG. 13B, for example. The detectionsignal Vdet_b obtained in this second period is represented by Equation(2) below. That is, basically, this detection signal Vdet_b alsoincludes a potential fluctuation component Va (=V1/(n+1)) due to the ACsignal source S, and a potential fluctuation component Vb(=Vn) due tonoise. It should be noted, however, that assuming WVGA (Wide VideoGraphics Array) as an example of resolution of the display pixels 20,then n=864, and assuming m=100, Equations (1) and (2) are (100/864)V1+Vnand (1/864)V1+Vn, respectively. Therefore, the value of the potentialfluctuation component Va in Equation (2) is (1/100) of the value of thepotential fluctuation component Va in Equation (1), and is sufficientlysmall relative to the potential fluctuation component Vb(Vn) due tonoise. That is, since the potential fluctuation component Va due to theAC signal source S in Equation (2) is negligibly small, the detectionsignal Vdet_b in Equation (2) can be considered to contain only thepotential fluctuation component Vb.

$\begin{matrix}\begin{matrix}{{Vdet\_ b} = {{V\; 1 \times \frac{Cp}{{n \times {Cp}} + {Cc}}} + {Vn}}} \\{= {{V\; 1 \times \frac{Cp}{( {n + 1} ){Cp}}} + {Vn}}} \\{= {{\frac{V\; 1}{n + 1} + {Vn}} \approx {Vn}}}\end{matrix} & (2)\end{matrix}$

Therefore, the signal processing section 84 and the frame memory 86generate a differential signal between the detection signal Vdet_aobtained in the first period, and the detection signal Vdet_b obtainedin the second period, in the manner as indicated by Equation (3) below.Thus, the potential fluctuation component Vb(Vn; noise signal) due tonoise is removed, and a differential signal made up of only thepotential fluctuation component Va (detection signal) due to the ACsignal source S is obtained. Accordingly, by performing a detection inthe coordinate extracting circuit 85 by using such a detection signalfrom which noise has been removed (reduced), the influence of noise(internal noise) contained in the detection signal Vdet due to an imagesignal writing operation can be removed (reduced), thereby enabling anaccurate detection.

$\begin{matrix}\begin{matrix}{{{Vdet\_ a} - {Vdet\_ b}} = ( {{{detection}\mspace{14mu}{signal}} +} } \\{ {{noise}\mspace{20mu}{signal}} ) - ( {{noise}\mspace{14mu}{signal}} )} \\{= ( {{detection}\mspace{14mu}{signal}} )}\end{matrix} & (3)\end{matrix}$

In the example shown in FIG. 11A, the position detection drive line L1and the display drive line L2 are each controlled so as to beline-sequentially driven one line at a time. On the other hand, in theexample shown in FIG. 11B, the position detection drive line L1 is setto be located at arbitrary positions (at random positions) within thecommon electrode 43 which differ from each other between the firstperiod and the first period. In the case of this configuration, theaverage position detection speed can be improved as compared with thecase of FIG. 11A.

Now, FIGS. 14A to 14C show an example of measured waveforms of: (A)detection signal+noise signal (corresponding to the detection signalVdet_a); (B) noise signal (corresponding to the detection signalVdet_b); and (C) detection signal (corresponding to a differentialsignal (Vdet_a−Vdet_b). It is apparent from FIGS. 14A to 14C that in thedifferential signal (Vdet_a−Vdet_b) obtained by the technique accordingto this embodiment, the influence of internal noise contained in thedetection signal Vdet is removed (reduced), thereby making it possibleto realize an accurate detection.

As described above, in this embodiment, the contact (proximity) positionof an object is detected on the basis of the detection signal Vdetobtained from the touch detection electrode in accordance with a changein electrostatic capacitance, and a detection is performed in thedetection circuit 8 on the basis of the detection signal Vdet_a obtainedfrom the position detection drive line L1 and the display drive line L2formed in the above-mentioned first period, and the detection signalVdet_b obtained from the display drive line L2 formed in the secondperiod different from the first period. Thus, a detection can beperformed while removing (reducing) the influence of the internal noisementioned above, for example, without using a shield layer as in therelated art. Therefore, it is possible to enhance the accuracy of objectdetection by a capacitive touch sensor.

Specifically, since a detection is performed on the basis of thedifferential signal (Vdet_a−Vdet_b) between the detection signal Vdet_aobtained in the first period and the detection signal Vdet_b obtained inthe second period, the effect as mentioned above can be obtained.

In addition, since the first period and the second period are setalternately at a time ratio of 1 to 1, noise detection is performedfrequently as compared with the case shown in FIGS. 15A, 15B describedbelow. Thus, the noise detection accuracy becomes higher to achieveimproved detection accuracy.

It should be noted that as shown in, for example, FIG. 15A(corresponding to FIG. 11A) and FIG. 15B (corresponding to FIG. 11B),the first period and the second period may be set alternately at a timeratio of x(x: an integer not smaller than 2) to 1. Then, the exampleshown in FIGS. 15A, 15B is configured such that a sequential drive isperformed with respect to the position detection drive line L1 withinthe first period, that is, the first period is made up of a plurality of(in this example, x) horizontal periods. In the case of thisconfiguration, position detection can be performed on the basis ofdetection results in the plurality of horizontal periods, thereby makingit possible to improve the accuracy of position detection as comparedwith the case shown in FIGS. 11A, 11B mentioned above.

In addition, detection modes may be switchable between the detectionmode (first detection mode) shown in FIGS. 11A, 11B, and the detectionmode (second detection mode) shown in FIGS. 15A, 15B. In the case ofthis configuration, it is possible to make adjustments as appropriate,such as which one of an improvement in noise detection accuracy (firstdetection mode) and an improvement in position detection accuracy(second detection mode) is to be emphasized in accordance with the usagecondition or application.

2. Second Embodiment

Next, a second embodiment of the present invention will be described.Unlike in the case of the above-mentioned first embodiment, in thisembodiment, a liquid crystal element of a transverse electric field modeis used as a display element.

[Example of Configuration of Display Device 1B]

FIG. 16 shows the cross-sectional structure of the main portion of adisplay device 1B with a touch sensor according to this embodiment.FIGS. 17A and 17B show the detailed configuration of a pixel substrate(pixel substrate 2B described later) in the display device 1B, of whichFIG. 17A shows a cross-sectional configuration, and FIG. 17B shows aplan configuration. FIGS. 18A and 18B show the perspective structure ofthe display device 1B. It should be noted that in these drawings,portions that are the same as those in the first embodiment mentionedabove are denoted by the same reference numerals, and descriptionthereof is omitted as appropriate.

The display device 1B according to this embodiment includes a pixelsubstrate 2B, a counter substrate 4B opposed to the pixel substrate 2B,and a liquid crystal layer 6 inserted between the pixel substrate 2B andthe counter substrate 4B.

The pixel substrate 2B has a TFT substrate 21, a common electrode 43disposed on the TFT substrate 21, and a plurality of pixel electrodes 22disposed in matrix on the common electrode 43 via an insulating film 23.In addition to display drivers and TFTs (not shown) for driving theindividual pixel electrodes 22, wires such as signal wires (sourcewires) 25 for supplying image signals to the individual pixel electrodesvia insulating layers 231, 232, and gate wires 26 for driving individualTFTs are formed on the TFT substrate 21 (FIG. 17). A detection circuit 8(FIG. 8) that performs a touch detection is also formed on the TFTsubstrate 21. The common electrode 43 also doubles as a sensor driveelectrode constituting a part of the touch sensor for performing a touchdetection, and corresponds to the drive electrode E1 shown in FIG. 1A.

The counter substrate 4B has a glass substrate 41, and a color filter 42formed on one surface of the glass substrate 41. A sensor detectionelectrode 44 is formed on the other surface of the glass substrate 41.Further, a polarizing plate 45 is disposed on the sensor detectionelectrode 44. The sensor detection electrode 44 constitutes a part ofthe touch sensor, and corresponds to the detection electrode E2 shown inFIG. 1A. As shown in FIG. 5, the sensor detection electrode 44 is splitinto a plurality of electrode patterns. The sensor detection electrode44 may be formed directly on the counter substrate 4B by a thin filmprocess, or may be indirectly formed. In this case, the touch detectionelectrode 44 may be formed on a film base (not shown), and this filmbase with the touch detection electrode 44 formed thereon may be affixedto the surface of the counter substrate 4B. In this case, it is alsopossible to affix the film base not only between the glass and thepolarizing plate but to the upper surface of the polarizing plate, andfurther, the film base may be formed within a film constituting thepolarizing plate.

A common drive signal Vcom having an AC rectangular waveform is appliedfrom the TFT substrate 21 to the common electrode 43. While this commondrive signal Vcom defines the display voltage of each pixel togetherwith a pixel voltage applied to each of the pixel electrodes 22, thecommon drive signal Vcom also doubles as a drive signal for the touchsensor, and corresponds to the AC rectangular wave Sg supplied from thedrive signal source S shown in FIGS. 1A and 1B.

The liquid crystal layer 6 modulates light passing through the liquidcrystal layer 6 in accordance with the state of the electric field. Forexample, a liquid crystal of a transverse electric field mode such as anFFS (Fringe Field Switching) mode or an IPS (In-plane Switching) mode isused for the liquid crystal layer 6.

The common electrode 43 in the pixel substrate 2B and the sensordetection electrode 44 in the counter substrate 4B are both of the sameconfiguration as those shown in FIG. 5, for example. Both the electrodesare formed as a plurality of electrode patterns extending so as to crosseach other.

Now, referring to FIGS. 18A and 18B, a more detailed description will begiven in this regard. In the liquid crystal element of the FFS mode inthis example, each of the pixel electrodes 22 patterned in a comb-teethform is disposed on the common electrode 43 formed on the pixelsubstrate 2B, via an insulating layer 23. An alignment film 26 is formedso as to cover the pixel electrode 22. The liquid crystal layer 6 issandwiched between the alignment film 26 and an alignment film 46 on thecounter substrate 4B side. Two polarizing plates 24, 45 are disposed ina crossed Nicol state. The rubbing direction of the two alignment films26, 46 coincides with the transmission axis of one of the two polarizingplates 24, 45. This example illustrates a case in which the rubbingdirection coincides with the transmission axis of the polarizing plate45 on the emission side. Further, the rubbing direction of the twoalignment films 26, 46, and the direction of the transmission axis ofthe polarizing plate 45 are set substantially parallel to the directionof extension (the longitudinal direction of the comb teeth) of the pixelelectrode 22 within a range in which the direction in which liquidcrystal molecules rotate is regulated.

[Operation/Effect of Display Device 1B]

Next, the operation and effect of the display device 1B according tothis embodiment will be described.

First, referring to FIGS. 18A and 18B and FIGS. 19A and 19B, a briefdescription will be given of the principle of display of a liquidcrystal element in the FFS mode. Here, FIGS. 19A and 19B show anenlarged cross section of the main portion of a liquid crystal element.In these drawings, FIGS. 19A and 19B shows the state of a liquid crystalelement when an electric field is not applied, and when an electricfield is applied, respectively.

In a state when no voltage is applied between the common electrode 43and the pixel electrodes 22 (FIGS. 18A, 19A), the axis of liquid crystalmolecules 61 forming the liquid crystal layer 6 is orthogonal to thetransmission axis of the polarizing plate 24 on the incidence side, andis parallel to the transmission axis of the polarizing plate 45 on theemission side. Thus, incident light h having passed through thepolarizing plate 24 on the incidence side reaches the polarizing plate45 on the emission side without being subject to any phase differencewithin the liquid crystal layer 6, and is absorbed by the polarizingplate 45, thus creating a black display. On the other hand, in a statewhen a voltage is applied between the common electrode 43 and the pixelelectrodes 22 (FIGS. 18B, 19B), the alignment direction of the liquidcrystal molecules 61 is rotated obliquely with respect to the directionof extension of the pixel electrodes 22 by a transverse electric field Egenerated between the pixel electrodes. At this time, the field strengthat the time of white display is optimized so that the liquid crystalmolecules 61 located at the center in the thickness direction of theliquid crystal layer 6 are rotated by approximately 45 degrees.Consequently, as the incident light h having passed through thepolarizing plate 24 on the incidence side passes through the liquidcrystal layer 6, the incident light h is subject to a phase difference,and becomes linearly polarized light rotated by 90 degrees, beforepassing through the polarizing plate 45 on the emission side, thuscreating a white display.

Next, a display control and a touch detection in the display device 1Bwill be described. Sine these operations are the same as the operationsin the first embodiment mentioned above, description thereof is omittedas appropriate.

A display driver (not shown) on the pixel substrate 2B supplies thecommon drive signal Vcom in a line sequential manner to each of theelectrode patterns of the common electrode 43. This display driver alsosupplies pixel signals (image signals) to the pixel electrodes 22 viathe source wires 25, and in synchronization with this, controls theswitching of the TFTs of the pixel electrodes via the gate wires 26 in aline sequential manner. Thus, an electric field in the transversedirection (direction parallel to the substrate) determined by the commondrive signal Vcom and each image signal is applied to the liquid crystallayer 6 for each pixel, thereby modulating the liquid crystal state. Inthis way, display by the so-called inversion drive is performed.

On the other hand, on the side of the counter substrate 4B, the commondrive signal Vcom is sequentially applied in a time division manner toeach of the electrode patterns of the common electrode 43. That is,charging and discharging are performed with respect to each of a row ofcapacitors C11 to C1 n formed at the intersections between the electrodepattern of the common electrode 43 to which the common drive signal Vcomhas been applied, and the individual electrode patterns of the sensordetection electrode 44. Then, a detection signal Vdet of a magnitudevarying with the capacitance value of the capacitor C1 is outputted fromeach of the electrode patterns of the sensor detection electrode 44. Ina state when a user's finger is not in touch with the surface of thecounter substrate 4B, the magnitude of this detection signal Vdet issubstantially constant. When a user's finger touches any one oflocations on the surface of the counter substrate 4B, the capacitor C2due to the finger is added to the capacitor C1 originally formed at thetouch location. As a result, the detection signal Vdet at the time whenthe touch location is scanned becomes smaller in value than at otherlocations. The detection circuit 8 (FIG. 8) compares this detectionsignal Vdet with the threshold voltage Vth, and determines the locationconcerned to be a touch location if the detection signal Vdet is lessthan the threshold voltage Vth. This touch location can be calculatedfrom the application timing of the common drive signal Vcom, and thedetection timing of the detection signal Vdet less than the thresholdvoltage Vth.

As described above, in this embodiment, as in the first embodimentmentioned above, a capacitive touch sensor is configured such that thecommon electrode 43 originally provided to the liquid crystal displayelement doubles as one of a pair of touch sensor electrodes including adrive electrode and a detection electrode, and the common drive signalVcom as a display drive signal is also used as a touch sensor drivesignal. Thus, it is necessary to additionally provide only the sensordetection electrode 44, and it is unnecessary to prepare a touch sensordrive signal. Therefore, the configuration is simple.

In this embodiment as well, the detection circuit 8 described above withreference to the first embodiment is provided. Thus, it is possible toattain the same effect through the same operation as that in the firstembodiment mentioned above. That is, it is possible to enhance theaccuracy of object detection in a display device including a capacitivetouch sensor without using a shield layer, for example.

In particular, this embodiment has a structure in which the commonelectrode 43 as a touch sensor drive electrode is provided on the pixelsubstrate 2B side (on top of the TFT substrate 21). Thus, supply of thecommon drive signal Vcom from the TFT substrate 21 to the commonelectrode 43 is extremely easy. In addition, necessary circuits,electrode patterns, wires, and the like can be concentrated in the pixelsubstrate 2, allowing for greater circuit integration. Therefore, thesupply path (contact conductive column 7) for the common drive signalVcom from the pixel substrate 2 side to the counter substrate 4 side,which is necessary in the first embodiment mentioned above, becomesunnecessary, thereby achieving simplification in structure.

In addition, as mentioned above, the common electrode 43 as a touchsensor drive electrode is provided on the pixel substrate 2B side, andthe source wires 25 and the gate wires 26 are also provided on the pixelsubstrate 2B. Thus, the structure according to this embodiment isparticularly susceptible to the influence of the internal noisedescribed above. For this reason, it can be said that the advantage ofperforming a detection by removing the influence of such internal noiseis particularly great in the case of the display device 1B according tothis embodiment.

While the detection circuit 8 (FIG. 8) may be formed in a peripheralregion (non-display region or rim region) on the counter substrate 4B,it is preferable to form the detection circuit 8 in a peripheral regionon the pixel substrate 2B. This is because forming the detection circuit8 on the pixel substrate 2B makes it possible to achieve integrationwith various circuit elements and the like for display control which areoriginally formed on the pixel substrate 2B.

Modifications of Second Embodiment

While in this embodiment the sensor detection electrode 44 is providedon the front surface side (the side opposite to the liquid crystal layer6) of the glass substrate 41, the following modifications are possible.

For example, as in a display device 1C shown in FIG. 20, in a countersubstrate 4C, the sensor detection electrode 44 may be provided on theliquid crystal layer 6 side with respect to the color filter 42.

Alternatively, as in a display device 1D shown in FIG. 21, in a countersubstrate 4D, the sensor detection electrode 44 may be provided betweenthe glass substrate 41 and the color filter 42. In this regard, in thecase of the transverse electric field mode, when there are electrodes inthe vertical direction, an electric field is applied in the verticaldirection to cause liquid crystals to rise, resulting in significantdeterioration in view angle or the like. Therefore, when the sensordetection electrode 44 is arranged via a dielectric such as the colorfilter 42 or the like, this problem can be significantly reduced.

3. Applications

Next, referring to FIGS. 22 to 26G, a description will be given ofapplications of the display device with a touch sensor described withreference to the embodiments and modifications mentioned above. Thedisplay device according to each of the above-mentioned embodiments andthe like can be applied to an electronic apparatus in all fields,including a television apparatus, a digital camera, a notebook personalcomputer, a portable terminal apparatus such as a portable telephone, ora video camera. In other words, the display device according to each ofthe above-mentioned embodiments and the like can be applied to anelectronic apparatus in all fields in which an externally inputtedpicture signal or an internally generated picture signal is displayed asan image or picture.

Application 1

FIG. 22 shows the outward appearance of a television apparatus to whichthe display device according to each of the embodiments and the likementioned above is applied. This television apparatus has, for example,a picture display screen section 510 including a front panel 511 and afilter glass 512. This picture display screen section 510 is formed bythe display device according to each of the embodiments and the likementioned above.

Application 2

FIGS. 23A and 23B show the outward appearance of a digital camera towhich the display device according to each of the embodiments and thelike mentioned above is applied. This digital camera has, for example, alight emitting section 521 for flashlight, a display section 522, a menuswitch 523, and a shutter button 524. The display section 522 is formedby the display device according to each of the embodiments and the likementioned above.

Application 3

FIG. 24 shows the outward appearance of a notebook personal computer towhich the display device according to each of the embodiments and thelike mentioned above is applied. This notebook personal computer has,for example, a main body 531, a keyboard 532 for making an inputoperation of characters or the like, and a display section 533 fordisplaying an image. The display section 533 is formed by the displaydevice according to each of the embodiments and the like mentionedabove.

Application 4

FIG. 25 shows the outward appearance of a video camera to which thedisplay device according to each of the embodiments and the likementioned above is applied. This video camera has, for example, a mainbody section 541, a lens 542 for shooting a subject which is provided onthe front side surface of the main body section 541, a start/stop switch543 to be operated when shooting, and a display section 544. The displaysection 544 is formed by the display device according to each of theembodiments and the like mentioned above.

Application 5

FIGS. 26A to 26G show the outward appearance of a portable telephone towhich the display device according to each of the embodiments and thelike mentioned above is applied. This portable telephone is formed bycoupling an upper housing 710 and a lower housing 720 together by acoupling section (hinge) 730, and has a display 740, a sub-display 750,a picture light 760, and a camera 770. The display 740 or thesub-display 750 is formed by the display device according to each of theembodiments and the like mentioned above.

4. Other Modification

While the present invention has been described above by way of severalembodiments, modifications, and applications, the present invention isnot limited to these embodiments and the like but various modificationsare possible.

For example, the above-mentioned embodiments and the like are directedto the case in which in the first and second periods, the display driveline L2 is also used as (made common with) the noise detection line.However, for example, the configuration shown in FIGS. 27A and 27B maybe employed. That is, in the first and second periods, the display driveline L2 and a noise detection line L3 may be separately provided.However, it can be said that making those lines common (double as eachother) as in the above-mentioned embodiments and the like is morepreferable because the circuit configuration and the control method aresimplified.

In addition, for example, the position detection drive line L1 and thedisplay drive line L2 (first drive line) in the first period, and thedisplay drive line L2 (second drive line) in the second period may belocated on substantially the same horizontal line within the commonelectrode 43. In the case of this configuration, the difference betweeninternal noises obtained in substantially the same pixel regions withinthe common electrode 43 is taken and removed, thereby avoiding locationdependence to achieve improved noise detection accuracy.

Further, while the above-mentioned second embodiment is directed to aliquid crystal element of the FFS mode as an example of transverseelectric field mode, the present invention can be similarly applied to aliquid crystal of the IPS mode.

In addition, the above-mentioned embodiments and the like are directedto the display device using a liquid crystal display element as adisplay element, the present invention is also applicable to displaydevices using other display elements, for example, an organic ELelement.

In addition, the above-mentioned embodiments and the like are directedto a case in which a touch sensor is built in a display device (adisplay device with a touch sensor). However, the touch sensor accordingto an embodiment of the present invention is not limited to this case.For example, the touch sensor may be applied to the outer side of thedisplay device (exterior touch sensor). Specifically, for example, atouch sensor 10 as shown in FIG. 28 may be provided on the outer side ofthe display device. The touch sensor 10 includes, for example, a pair ofinsulating substrates 411, 412 made of glass or the like, a sensor driveelectrode (touch drive electrode) 430 formed between these substrates, asensor detection electrode 44, and an insulating layer 230. The sensordrive electrode 430 is formed on the insulating substrate 411, and isapplied with a drive signal for the touch sensor. The sensor detectionelectrode 44 is formed on the insulating substrate 412. As in theabove-mentioned embodiments and the like, the sensor detection electrode44 is an electrode for obtaining a detection signal Vdet. The insulatinglayer 230 is formed between the sensor drive electrode 430 and thesensor detection electrode 44. It should be noted that the perspectivestructure of the touch sensor 10 is the same as that according to theabove-mentioned embodiments and the like shown in FIG. 5 and the like,for example. In addition, the circuit configurations and the like of thedrive signal source S, the detection circuit 8, and the timing controlsection 9 are also the same as those in the above-mentioned embodimentsand the like shown in FIG. 8. In the touch sensor 10 configured asdescribed above, for example, a position detection drive line L1 and anoise detection drive line L3 as shown in FIG. 29 may be employed. Thatis, the position detection drive line L1 and the noise detection driveline L3 may be formed from unitary common electrodes, such as commonelectrodes 430-1, 430-3, 430-5, 430-7, and the like, and 430-2, 430-4,430-6, 430-8, and the like. Although the touch sensor 10 configured asdescribed above may not necessarily be provided with the noise detectiondrive line L3, it is preferable that the noise detection drive line L3be provided from the viewpoint of improved detection accuracy or thelike.

Furthermore, the series of processes described above with reference tothe above-mentioned embodiments and the like can be either executed byhardware or executed by software. If the series of processes is to beexecuted by software, a program constituting the software is installedinto a general purpose personal computer or the like. Such a program maybe pre-recorded on a recording medium built in the computer.

In accordance with the touch sensor, the display device, and theelectronic apparatus according to an embodiment of the presentinvention, the contact or proximity position of an object is detected onthe basis of the detection signal obtained from the touch detectionelectrode in response to a change in electrostatic capacitance. Inaddition, the touch detection circuit performs a detection on the basisof the first detection signal obtained from the first drive line formedin the first period, and the second detection signal obtained from thesecond drive line having a line width smaller than the line width of thefirst drive line. Thus, a detection can be performed while reducing theinfluence of the internal noise mentioned above, for example, withoutusing a shield layer as in the related art. Therefore, it is possible toimprove the accuracy of object detection in a capacitive touch sensor.

It should be understood by those skilled in the art that variousmodifications, combinations, sub-combinations and alterations may occurdepending on design requirements and other factors insofar as they arewithin the scope of the appended claims or the equivalents thereof.

What is claimed is:
 1. A touch sensor comprising: a sensor electrodehaving an electrostatic capacitance for touch detection; a touchdetection circuit that performs a detection of a contact or proximityposition of an object, on the basis of a detection signal obtained fromthe sensor electrode by applying a touch sensor drive signal to thesensor electrode, wherein the sensor electrode is split into a pluralityof electrode patterns in a stripe shape, and application of the touchsensor drive signal to part of the plurality of electrode patternscauses a drive line to be formed at that time, the touch detectioncircuit performs the detection on the basis of a first detection signalobtained from a first drive line formed in a first period, and a seconddetection signal obtained from a second drive line formed in a secondperiod different from the first period, and the touch detection circuitperforms the detection on the basis of a differential signal between thefirst detection signal and the second detection signal.
 2. The touchsensor according to claim 1, wherein the first period and the secondperiod are set alternately at a time ratio of 1 to
 1. 3. The touchsensor according to claim 1, wherein: the first period and the secondperiod are set alternately at a time ratio of n (n: an integer notsmaller than 2) to 1; the first drive line includes a position detectiondrive line; and within the first period, a sequential drive is performedwith respect to the position detection drive line.
 4. The touch sensoraccording to claim 3, wherein the first drive line includes the positiondetection drive line and a noise detection drive line having a linewidth equal to the line width of the second drive line.
 5. The touchsensor according to claim 1, wherein: detection modes can be switchedbetween a first detection mode and a second detection mode; the firstdetection mode is a mode in which the first period and the second periodare set alternately at a time ratio of 1 to 1; and the second detectionmode is a mode in which the first period and the second period are setalternately at a time ratio of n (n: an integer not smaller than 2) to1, the first drive line includes a position detection drive line, and asequential drive is performed with respect to the position detectiondrive line within the first period.
 6. The touch sensor according toclaim 5, wherein the first drive line includes the position detectiondrive line and a noise detection drive line having a line width equal tothe line width of the second drive line.
 7. The touch sensor accordingto claim 1, wherein: the first period and the second period are setalternately in a time division manner; the first drive line includes aposition detection drive line; and the position detection drive line isset at arbitrary positions within the sensor electrode which differ fromeach other between the first period and the second period.
 8. The touchsensor according to claim 7, wherein the first drive line includes theposition detection drive line and a noise detection drive line having aline width equal to the line width of the second drive line.
 9. Thetouch sensor according to claim 1, wherein the first drive line in thefirst period, and the second drive line in the second period are locatedon substantially the same line within the sensor electrode.
 10. Adisplay device comprising: a plurality of display pixel electrodes; adisplay function layer having an image display function; a displaycontrol circuit that controls image display on the basis of an imagesignal so as to apply a display drive voltage to the display pixelelectrodes and to cause the display function layer to exert the imagedisplay function, on the basis of an image signal; a sensor electrodehaving an electrostatic capacitance for touch detection; and a touchdetection circuit that performs a detection of a contact or proximityposition of an object, on the basis of a detection signal obtained fromthe sensor electrode, by using the display drive voltage applied to thesensor electrode by the display control circuit as a touch sensor drivesignal, wherein the sensor electrode is split into a plurality ofelectrode patterns in a stripe shape, and application of the touchsensor drive signal to part of the plurality of electrode patternscauses a drive line to be formed at that time, the touch detectioncircuit performs the detection on the basis of a first detection signalobtained from a first drive line formed in a first period, and a seconddetection signal obtained from a second drive line formed in a secondperiod different from the first period, and the touch detection circuitperforms the detection on the basis of a differential signal between thefirst detection signal and the second detection signal.
 11. The displaydevice according to claim 10, wherein: the first drive line includes aposition detection drive line and a noise detection drive line having aline width equal to the line width of the second drive line; and thenoise detection drive line and the second drive line are each madecommon with an image display drive line for performing image display bythe display control circuit.
 12. The display device according to claim10, wherein the display control circuit performs a sequential drive withrespect to the drive line formed as a batch of two or more electrodepatterns of the plurality of electrode patterns.
 13. The display deviceaccording to claim 10, further comprising: a circuit board on which thedisplay control circuit is formed; and a counter substrate disposed inopposition to the circuit board, wherein the display pixel electrodesare disposed on a side of the circuit board close to the countersubstrate, and the display function layer is inserted between thedisplay pixel electrodes on the circuit board.
 14. The display deviceaccording to claim 13, wherein the display function layer is a liquidcrystal layer.
 15. The display device according to claim 10, furthercomprising: a circuit board on which the display control circuit isformed; and a counter substrate disposed in opposition to the circuitboard, wherein the display pixel electrodes are laminated on the circuitboard via an insulating layer, and the display function layer isinserted between the display pixel electrodes on the circuit board, andthe counter substrate.
 16. The display device according to claim 15,wherein the display function layer is a liquid crystal layer, andperforms liquid crystal display in a transverse electric field mode. 17.An electronic apparatus comprising a display device with a touch sensor,the display device including: a plurality of display pixel electrodes; adisplay function layer having an image display function; a displaycontrol circuit that controls image display on the basis of an imagesignal so as to apply a display drive voltage to the display pixelelectrodes to cause the display function layer to exert the imagedisplay function, on the basis of an image signal; a sensor electrodehaving an electrostatic capacitance for touch detection; and a touchdetection circuit that performs a detection of a contact or proximityposition of an object, on the basis of a detection signal obtained fromthe sensor electrode, by using the display drive voltage applied to thesensor electrode by the display control circuit as a touch sensor drivesignal, wherein the sensor electrode is split into a plurality ofelectrode patterns in a stripe shape, and application of the touchsensor drive signal to part of the plurality of electrode patternscauses a drive line to be formed at that time, the touch detectioncircuit performs the detection on the basis of a first detection signalobtained from a first drive line formed in a first period, and a seconddetection signal obtained from a second drive line formed in a secondperiod different from the first period and having a smaller line widththan the first drive line, and the touch detection circuit performs thedetection on the basis of a differential signal between the firstdetection signal and the second detection signal.
 18. The electronicapparatus according to claim 17, wherein: the first drive line includesa position detection drive line and a noise detection drive line havinga line width equal to the line width of the second drive line; and thenoise detection drive line and the second drive line are each madecommon with an image display drive line for performing image display bythe display control circuit.
 19. The electronic apparatus according toclaim 17, wherein the display control circuit performs a sequentialdrive with respect to the drive line formed as a batch of two or moreelectrode patterns of the plurality of electrode patterns.
 20. Theelectronic apparatus according to claim 17, wherein: the first periodand the second period are set alternately in a time division manner; thefirst drive line includes a position detection drive line; and theposition detection drive line is set at arbitrary positions within thesensor electrode which differ from each other between the first periodand the second period.